Cooling and crystallization ponds are used in the solution mining industry to provide relatively adaptable and low energy cost salt production solutions. The use of cooling ponds is especially suited for areas where land is not a limiting factor, and the weather is favourable for cooling (i.e. low ambient temperature and low precipitation). Moreover, cooling ponds do not require major investment and maintenance, making it an attractive technology for the solution mining industry.
For potash solution mining, the potash is dissolved from deep underground using hot brine and the solution is pumped to the surface for processing into the potash product. The processing of the hot brine may include cooling and crystallization in a pond. The hot brine is typically unsaturated in KCl and NaCl as it is pumped into the inlet of the pond, although saturated inlet brine conditions can also exist with respect to both NaCl and KCl. As it flows through the pond from the inlet to the outlet, the brine is cooled by a number of modes, including radiative, convective and evaporative losses from the pond surface, and conduction losses to the ground. Evaporation will also cause concentration of the brine.
As the brine cools, the solubility of KCl is reduced until saturation is achieved, and with further cooling KCl crystallizes out of solution. Meanwhile, the NaCl concentration remains nearly at or slightly below saturation levels and so does not crystallize out. The KCl crystals fall to the bottom of the pond and are periodically recovered for processing into the potash product.
The configuration of a pond and the brine inflow operating parameters determine the flow patterns which affect the overall performance of the cooling pond. Typical cooling ponds include one or more channels separated by dikes or weirs, each dike or weir having a small gap through which the brine is permitted to flow between the adjacent channels. The inventors have discovered that conventional pond design may lead to poor flow distribution within the pond, and the inventors believe that this poor flow distribution has a detrimental effect on the efficiency of heat transfer and mineral salt productivity (e.g. KCl). Furthermore, the inventors believe that past attempts to improve cooling pond performance without addressing flow distribution have resulted in failure. For example, attempts to improve cooling by simply enlarging the surface area of cooling ponds have not necessarily improved the recovery of salts. Also, simply increasing the flow velocity of the brine through the pond has been found to increase the salt production, but decrease the yield (or productivity).
Therefore, there is a continued need to improve the performance of ponds for cooling and crystallizing salts from brine.